DOCSLIB.ORG

The T2K Experiment Daniel I

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The T2K Experiment Daniel I The T2K Experiment Daniel I. Scully University of Warwick, Department of Physics, Coventry. UK Abstract. T2K is a long-baseline neutrino oscillation experiment built to make precision measurements of q13, q23 and 2 Dm 32. It achieves this by utilising an off-axis, predominantly nm , neutrino beam from J-PARC to Super-Kamiokande, and a near detector complex which constrains the beam’s direction, flux, composition and energy. To date T2K has published nm -disappearance and ne-appearance results, the latter excluding q13 = 0 at over 3s and therefore constituting first evidence for ne-appearance in a nm beam. In addition to oscillation physics, the on-axis (INGRID) and off-axis (ND280) near detectors provide the capability for a broad neutrino-nucleus interaction physics programme at neutrino energies below 1GeV. Keywords: T2K, ND280, neutrino, oscillations, cross sections PACS: 14.60.Lm, 13.15.+g T2K OVERVIEW The T2K experiment [1], based in Japan, is a long-baseline neutrino oscillation experiment built to make precision 2 measurements of q13, q23 and Dm 32. The first stage of the experiment is a neutrino beam generated at the J-PARC proton accelerator facility. 30 GeV protons are collided with a graphite target and three magnetic horns focus the resulting positive pions and kaons down a 110m decay tunnel. These decay in flight to produce a beam of predominantly nm , though some n m (≈ 6%), ne (≈ 1%) and ne (< 1%) are also produced (Figure 1a)[2]. (a) The contribution of each neutrino flavour to the flux through (b) The effect on the neutrino energy spectrum of moving off the ND280. beam axis. FIGURE 1. The J-PARC Neutrino Beam The beam then travels 295km through Japan to the famous Super-Kamiokande detector [3]. Located under 1000m of Mt. Ikenoyama, Super-Kamiokande is a 50kT cylindrical water-Cherenkov detctor the inner part of which is instru- mented with ≈ 13000 photo-multiplier tubes (PMTs). These PMTs image the Cherenkov rings produced by charged particles eminating from neutrino interactions in the water, and have sufficient timing and directional resolution to identify neutrinos which have originated in the T2K beam (Figures 2a and 2b). Additionally, Super-Kamiokande’s particle identification separates the primary Cherenkov ring according to whether it showered or not which, for charged-current interactions, allows it to discriminate between nm and ne events (Figure 2c). However, because showering electrons appear almost identical to showering photons, neutral-current p0 production is an important background. The T2K experiment is also noteworthy as the world’s first off-axis neutrino beam: the J-PARC beam is directed such that Super-Kamiokande lies 2.5◦ off the beam’s axis. There are two reasons for doing this, which are illustrated in Figure 1b. First, the neutrino flux is increased at the optimal energy for ne appearance at Super-Kamiokande (≈ 0:6GeV). Second, a substantial fraction of the higher energy neutrinos are removed - neutrinos which do not contribute to the oscillation signal but can generate significant neutral-current backgrounds. In addition to the beam and far-detector, T2K includes a near detector complex 280m downstream of the beam target. It contains two detectors: the on-axis “INGRID” was built primarily for measuring the beam normalisation and direction, while the off-axis “ND280” measures the beam’s composition and energy spectrum in the direction of Super-Kamiokande as well as performing neutrino-nucleus interaction physics analyses. INGRID The INGRID detector consists of 16 identical 1.24m square modules. The modules are positioned in a cross, centred on the beam axis, formed of horizontal and vertical arms containing 7 modules each. Two additional modules are then placed in the left and right top-corners (Figure 3a). This placement allows INGRID to effectively measure the beam’s profile and hence direction with sub-milliradian precision (Figure 4). Each module is formed of 9 × 65mm-thick iron plates sandwiched between 11 x-y planes of plastic scintillator bars (50mm × 10mm). Such coarse-grained readout and thick dead-regions means that INGRID’s reconstruction is essentially limited to measuring the vertex position and primary-lepton angle for charged-current nm interactions. There is however, an additional scintillator-only module placed between the two central modules which can resolve a recoil proton from nm CCQE interactions. In addition to its beam profiling INGRID is also capable of some interaction physics, for example a nm Inclusive charged-current measurement. Such a measurement would be able to exploit the fact that modules at different off-axis angles each see a different energy spectrum from the same beam. ND280 The off-axis near-detector, “ND280” (Figure 3b) was built to measure the beam composition and energy spectrum in the direction of Super-Kamiokande. It can also perform a full programme of neutrino interaction physics, both to reduce systematics in the oscillation measurement and as a valid physics goal in its own right. One of the key interaction measurements for input to the oscillation analysis will be neutral-current p0 production which, as discussed earlier, is an important background for ne-appearance at Super-Kamiokande. The upstream-most component of ND280, the Pi-Zero Detector (P0D) was built with this purpose in mind. The central part of the P0D (a) The time from trigger of events (b) The reconstructed angle w.r.t the (c) The cut placed on Super- from the ne selection. The 8-bunch T2K beam of events from the nm selec- Kamiokande’s Particle Id parameter as structure of the T2K beam can be seen tion. part of the ne selection. clearly. FIGURE 2. Data-MC comparissons for event selections at Super-Kamiokande. (a) Layout of the INGRID modules looking downstream. The (b) Exploded view of the ND280 off-axis near detector. The cross shape is centred on the beam’s axis. beam enters from the left side of the diagram. FIGURE 3. Near Detectors (a) The stability of the beam direction as determined in INGIRD, (b) The beam profile fitted to data from the horizontal and verti- giving sub-milliradian precision. cal INGRID modules. FIGURE 4. Determining the beam direction using INGRID alternates water targets (for maximum applicability to Super-Kamiokande) with xy-modules of triangular plastic scintillator bars and brass foils to encourage photon conversion. Up and downstream of the central target region are calorimeter regions where the plastic scintillator modules are instead interleaved with lead sheets to further improve photon containment. The water targets can be drained and re-filled at will to provide an additional control of the water contribution to the interaction rate in the P0D. The second interaction targets are the two Fine Grained Detectors (FGDs) which are built with square plastic scintillator bars. The upstream FGD1 is built solely from 15 xy-modules of scintillator bars and is the primary target region for most of ND280’s physics analyses. Meanwhile in FGD2, 8 of those modules are replaced with non-drainable water targets such that the two FGDs have almost identical target masses. The 10 mm-square scintillator bars provide sufficient resolution to track secondary final-state particles while also having enough mass to ensure a good event rate. Downstream of each of the P0D and two FGDs is a gas Time Projection Chamber (TPC) for high-resolution tracking π × ­3 4.0 10 Normal hierarchy T2K 1.431E+20 POT (GENIE), Feldman­Cousins 90% CL (stat) T2K 1.431E+20 POT (GENIE), Feldman­Cousins 90% CL (stat+syst) π 2 ­3 2 /2 ∆ × T2K 1.431E+20 POT (NEUT), Feldman­Cousins 90% CL (stat) m32 = 2.4 10 eV 3.5 sin2 2θ = 1.0 T2K 1.431E+20 POT (NEUT), Feldman­Cousins 90% CL (stat+syst) 23 MINOS 2011 (7.25E+20 POT), 90% CL ) 4 /c 2 CP 0 3.0 δ Best fit to T2K data | (eV 2 23 2.5 m 68% CL ∆ ­π/2 | 90% CL 2.0 ­π 0 0.1 0.2 0.3 0.4 0.5 0.6 1.5 0.75 0.80 0.85 0.90 0.95 1.00 2 θ sin22θ sin 2 13 23 2 2 2 (a) The best-fit value, 68% and 90% CL regions for sin 2q13 (b) Best-fit point and 90% CL contours for sin 2q23 vs Dm 23 shown as a function of the assumed value of dCP compared to MINOS (black). Contours are shown for both the , for a normal mass hierarchy. Genie (blue) and Neut (red) generators, with (solid) and without (dashed) systematic errors. FIGURE 5. Oscillation results of particles leaving the target detectors. It’s sub-millimetre position resolution makes the TPC essential to analysis requiring charge and momentum determination from curvature, and particle identification from energy loss. Together, the P0D, FGDs and TPCs are surrounded on all but the upstream-face by electromagnetic-calorimeters (ECals). The FGDs and TPCs are surrounded by the “Tracker ECals” which each alternate over 30 1.75 mm-thick lead sheets with layers of 40 mm × 10 mm plastic scintillator bars with 1.75 mm-thick lead sheets. These provide containment of escaping particles, additional particle identification and conversion of photons. The ECals surrounding the P0D are much smaller, containing only 6 scintillator layers with 4 mm-thick lead sheets, since they need only veto incoming backgrounds and detect photons escaping at high angle from the P0D. All of these subsystems are then encased within the 0.2 T magnet, formerly used by the NOMAD and UA1 experiments. Gaps between the iron plates of the magnet yoke are instrumented with the Side Muon Ranging Detector (SMRD) - slabs of plastic scintillator which provide the detector’s cosmic trigger, but can also contribute to the reconstruction of escaping muons.
Load more

Recommended publications
  • CERN Courier – Digital Edition Welcome to the Digital Edition of the January/February 2013 Issue of CERN Courier – the First Digital Edition of This Magazine
    I NTERNATIONAL J OURNAL OF H IGH -E NERGY P HYSICS CERNCOURIER WELCOME V OLUME 5 3 N UMBER 1 J ANUARY /F EBRUARY 2 0 1 3 CERN Courier – digital edition Welcome to the digital edition of the January/February 2013 issue of CERN Courier – the first digital edition of this magazine. CERN Courier dates back to August 1959, when the first issue appeared, consisting of eight black-and-white pages. Since then it has seen many changes in design and layout, leading to the current full-colour editions of more than 50 pages on average. It went on the web for the High luminosity: first time in October 1998, when IOP Publishing took over the production work. Now, we have taken another step forward with this digital edition, which provides yet another means to access the content beyond the web the heat is on and print editions, which continue as before. Back in 1959, the first issue reported on progress towards the start of CERN’s first proton synchrotron. This current issue includes a report from the physics frontier as seen by the ATLAS experiment at the laboratory’s current flagship, the LHC, as well as a look at work that is under way to get the most from this remarkable machine in future. Particle physics has changed a great deal since 1959 and this is reflected in the article on the emergence of QCD, the theory of the strong interaction, in the early 1970s. To sign up to the new issue alert, please visit: http://cerncourier.com/cws/sign-up To subscribe to the print edition, please visit: http://cerncourier.com/cws/how-to-subscribe LHC PHYSICS FERMILAB FRONTIER Using monojets Oddone to retire to point the way after eight PHYSICS EDITOR: CHRISTINE SUTTON, CERN to new physics fruitful years Opening up DIGITAL EDITION CREATED BY JESSE KARJALAINEN/IOP PUBLISHING, UK p7 p35 interdisciplinarity p33 CERNCOURIER www.
    [Show full text]
  • Switching Neutrinos
    Research in Progress Physics Fl avor- -Switching Neutrinos rof. Ewa Rondio from the National P Center for Nuclear Research (NCBJ) explains the nature of neutrinos, the measurements taken by the Super-Kamiokande detector, and the involvement of Polish scientists in the project. MIJAKOWSKI PIOTR ACADEMIA: What are neutrinos? What is the difference between the neutrinos that PROF. EWA RONDIO: Literally translated, the word come from space and the neutrinos created on Earth? “neutrino” means “little neutral one.” The name was Neutrinos arriving from space are almost as abundant first suggested when the existence of neutrinos was as photons in the cosmic background radiation, but proposed to patch up the law of conservation of en- their energies are so small that we’re unable to detect ergy. It had turned out that without postulating their them. We can’t see them, even though there are so existence we could not explain why the spectrum of many of them. We can only observe higher-energy energy in beta decay is continuous, whereas two-body neutrinos, for example those arriving from the Sun. decay should give a single constant value. Back then, At first glance, they do not differ in any way from that postulate was considered very risky, because it those made on Earth. However, they have somewhat was believed that such particles would be impossible different energies. Also, those arriving from space are to observe. Experimental physicists have nowadays predominantly neutrinos, whereas those we produce managed that, although it took them quite a long time. on Earth produce are chiefly antineutrinos.
    [Show full text]
  • Kavli IPMU Annual 2014 Report
    ANNUAL REPORT 2014 REPORT ANNUAL April 2014–March 2015 2014–March April Kavli IPMU Kavli Kavli IPMU Annual Report 2014 April 2014–March 2015 CONTENTS FOREWORD 2 1 INTRODUCTION 4 2 NEWS&EVENTS 8 3 ORGANIZATION 10 4 STAFF 14 5 RESEARCHHIGHLIGHTS 20 5.1 Unbiased Bases and Critical Points of a Potential ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙20 5.2 Secondary Polytopes and the Algebra of the Infrared ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙21 5.3 Moduli of Bridgeland Semistable Objects on 3- Folds and Donaldson- Thomas Invariants ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙22 5.4 Leptogenesis Via Axion Oscillations after Inflation ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙23 5.5 Searching for Matter/Antimatter Asymmetry with T2K Experiment ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ 24 5.6 Development of the Belle II Silicon Vertex Detector ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙26 5.7 Search for Physics beyond Standard Model with KamLAND-Zen ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙28 5.8 Chemical Abundance Patterns of the Most Iron-Poor Stars as Probes of the First Stars in the Universe ∙ ∙ ∙ 29 5.9 Measuring Gravitational lensing Using CMB B-mode Polarization by POLARBEAR ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ 30 5.10 The First Galaxy Maps from the SDSS-IV MaNGA Survey ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙32 5.11 Detection of the Possible Companion Star of Supernova 2011dh ∙ ∙ ∙ ∙ ∙ ∙
    [Show full text]
  • Long Baseline Neutrino Oscillation Experiments 1 Introduction 2
    Long Baseline Neutrino Oscillation Experiments Mark Thomson Cavendish Laboratory Department of Physics JJ Thomson Avenue Cambridge, CB3 0HE United Kingdom 1 Introduction In the last ten years the study of the quantum mechanical e®ect of neutrino os- cillations, which arises due to the mixing of the weak eigenstates fºe; º¹; º¿ g and the mass eigenstates fº1; º2; º3g, has revolutionised our understanding of neutrinos. Until recently, this understanding was dominated by experimental observations of at- mospheric [1, 2, 3] and solar neutrino [4, 5, 6] oscillations. These measurements have been of great importance. However, the use of naturally occuring neutrino sources is not su±cient to determine fully the flavour mixing parameters in the neutrino sector. For this reason, many of the current and next generation of neutrino experiments are based on high intensity accelerator generated neutrino beams. The ¯rst generation of these long-baseline (LBL) neutrino oscillation experiments, K2K, MINOS and CNGS, are the main subject of this review. The next generation of LBL experiments, T2K and NOºA, are also discussed. 2 Theoretical Background For two neutrino weak eigenstates fº®; º¯g related to two mass eigenstates fºi; ºjg, by a single mixing angle θij, it is simple to show that the survival probability of a neutrino of energy Eº and flavour ® after propagating a distance L through the vacuum is à ! 2 2 2 2 1:27¢mji(eV )L(km) P (º® ! º®) = 1 ¡ sin 2θij sin ; (1) Eº(GeV) 2 2 2 where ¢mji is the di®erence of the squares of the neutrino masses, mj ¡ mi .
    [Show full text]
  • A Brief Overview of Neutrino Oscillabon Results and Future Prospects
    A brief overview of neutrino oscillaon results and future prospects Trevor Stewart On behalf of the T2K collaboraon Rutherford Appleton Laboratory ICNFP 2016 01/01/2015 Trevor Stewart, RAL 1 The Nobel Prize in Physics 2015 Takaaki Kajita, Arthur B. McDonald “for the discovery of neutrino oscillaons, which shows that neutrinos have mass" 06/07/2016 Trevor Stewart, RAL 2 Intoduc2on • This talk will discuss recent neutrino oscillaon results and how they contribute to our overall understanding of the physics of neutrinos • Will present results from current experiments such as T2K, NOνA, Daya Bay, RENO, and Double Chooz • Discuss future experiments such as Hyper- Kamiokande, DUNE, and JUNO • If I do not men2on your favourite experiment then please forgive me, it is for the sake of brevity 01/01/2015 Trevor Stewart, RAL 3 Two-flavour neutrino oscillaons ⌫ cos✓ sin✓ ⌫ • e = 1 Two sets of eigenstates for ⌫µ sin✓ cos✓ ⌫2 neutrinos ✓ ◆ ✓− ◆✓ 2 ◆ - Flavour states which 2 2 ⎛ Δm L ⎞ P(ν →ν ) = sin (2θ )sin ⎜ ⎟ interact µ e ⎜ 4E ⎟ ∆m2 = m2 m2 ⎝ ⎠ - Mass states which 2 − 1 propagate ⌫µ ⌫1, ⌫2 ⌫µ or ⌫e • Measure • Result probabili2es – Mixing angle(s) – Disappearance – Mass differences – Appearance 01/01/2015 Trevor Stewart, RAL 4 The Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix ⌫e ⌫1 • Unfortunately things are not as ⌫ = U ⌫ 0 µ1 0 21 simple as the 2-flavour mixing ⌫⌧ ⌫3 shown on the previous slide @ A @ A • 3-flavour mixing Flavour eigenstates Mass eigenstates - Three independent mixing (coupling to the W, Z) (definite masses) angles and CP violang
    [Show full text]
  • Final Report for Studies in Elementary Particle Physics for the Period February 1, 2010 to April 30, 2013 Virginia Tech Tasks A, B, and N
    Final Report for Studies in Elementary Particle Physics for the period February 1, 2010 to April 30, 2013 Virginia Tech Tasks A, B, and N Leo Piilonen Tatsu Takeuchi Djordje Minic Jonathan Link Center for Neutrino Physics, Department of Physics Virginia Polytechnic Institute and State University Blacksburg VA 24061-0435 Principal Investigator: Leo Piilonen Center for Neutrino Physics, Department of Physics 125 Robeson Hall Virginia Tech Blacksburg VA 24061-0435 (540)231-7472 [email protected] Office of High Energy Physics DOE/Science Program Office Technical Contact: Dr. Alan Stone DOE Grant Number: DE-FG05-92ER40709 1 Overview of the Virginia Tech HEP Program and Group This final report of DOE Grant DE-FG05-92ER40709 awarded to the Virginia Tech HEP group covers the period February 1, 2010 through April 30, 2013. The HEP program at Virginia Tech supported by this grant is organized into three tasks: A for theory (Profs. Tatsu Takeuchi and Djordje Minic), B for heavy flavor physics with the Belle and Belle II experiments (Prof. Leo Piilonen), and N for neutrino physics (Profs. Jonathan Link and Piilonen). There are several other HEP faculty members at Virginia Tech who were not supported by this grant through April 30, 2012 with whom we collaborated. Prof. Patrick Huber works in neutrino phenomenology and is supported by a separate ECRA grant from DOE. Prof. Eric Sharpe col- laborates with Minic and Takeuchi and is supported by the NSF. Prof. Camillo Mariani joined Virginia Tech in August 2012 as our newest neutrino experimentalist. Prof. Bruce Vogelaar is another neutrino experimentalist supported by the NSF; he collaborated with the late Prof.
    [Show full text]
  • Research in Physics 2008-2013
    Research in Physics 2008-2013 Theoretical Physics .................................................................................................................................. 1 Condensed Matter, Materials and Soft Matter Physics ....................................................................... 38 Nanoscale Physics Cluster ........................................................................................................... 38 Magnetic Resonance Cluster ...................................................................................................... 96 Materials Physics Cluster .......................................................................................................... 121 Astronomy and Astrophysics (A&A) .................................................................................................... 172 Elementary Particle Physics (EPP) ....................................................................................................... 204 Centre for Fusion Space and Astrophysics (CFSA) .............................................................................. 247 Theoretical Physics Theoretical Physics 10 Staff; 10 PDRAs; 22 PhDs; 219 articles; 2472 citations; £2.9 M grant awards; £1.1 M in-kind; 20 PhDs awarded The main themes of research in Theoretical Physics are: Molecular & Materials Modelling; Complexity & Biological Physics; Quantum Condensed Matter. The Theory Group has a breadth of expertise in materials modelling, esp. in molecular dynamics and electronic structure calculations.
    [Show full text]
  • Deliberation Document on the 2020 Update European Strategy
    DELIBERATION DOCUMENT ON THE 2020 UPDATE OF THE EUROPEAN STRATEGY FOR PARTICLE PHYSICS The European Strategy Group _Preface The first European Strategy for Particle Physics (hereinafter referred to as “the Strategy”), consisting of seventeen Strategy statements, was adopted by the CERN Council at its special session in Lisbon in July 2006. A first update of the Strategy was adopted by the CERN Council at its special session in Brussels in May 2013. This second update of the Strategy was formulated by the European Strategy Group (ESG) (Annex 1) during its six-day meeting in Bad Honnef in January 2020. The resolution on the 2020 Update of the European Strategy for Particle Physics was adopted at the 199th Session of the CERN Council on 19 June 2020. The ESG was assisted by the Physics Preparatory Group (Annex 2), which had provided scientific input based on the material presented at a four-day Open Symposium held in Granada in May 2019, and on documents submitted by the community worldwide. In addition, six working groups (Annex 3) were set up within the ESG to address the following points: Social and career aspects for the next generation; Issues related to Global Projects hosted by CERN or funded through CERN outside Europe; Relations with other groups and organisations; Knowledge and Technology Transfer; Public engagement, Education and Communication; Sustainability and Environmental impact. Their conclusions were discussed at the Bad Honnef meeting. This Deliberation Document was prepared by the Strategy Secretariat. It provides background information underpinning the Strategy statements. Recommendations to the CERN Council made by the Working Groups for possible modifications to certain organisational matters are also given.
    [Show full text]
  • Neutrino Experiments Come Closer to Seeing
    Neutrino Experiments Come Closer to Seeing The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Formaggio, Joseph. “Neutrino Experiments Come Closer to SeeingCPViolation.” Physics 7 (February 10, 2014). © 2014 American Physical Society As Published http://dx.doi.org/10.1103/PHYSICS.7.15 Publisher American Physical Society (APS) Version Final published version Citable link http://hdl.handle.net/1721.1/121059 Terms of Use Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. Physics 7, 15 (2014) Viewpoint Neutrino Experiments Come Closer to Seeing CP Violation Joseph A. Formaggio Massachusetts Institute of Technology, Cambridge, MA 02139, USA Published February 10, 2014 The T2K experiment has measured the largest number of events associated with muon neutrinos oscillating into electron neutrinos, an important step toward seeing CP violation in neutrino inter- actions. Subject Areas: Particles and Fields A Viewpoint on: Observation of Electron Neutrino Appearance in a Muon Neutrino Beam K. Abe emet al./em (T2K Collaboration) Physical Review Letters 112, 061802 2014 – Published February 10, 2014 Charge-parity (CP ) violation—evidence that the laws sends a beam of muon neutrinos over a long distance to- of physics are different for particles and antiparticles—is ward a detector that searches for the presence of electron often invoked as a “must” to explain why we observe neutrinos. Since the total number of electron neutrinos more matter than antimatter in the universe.
    [Show full text]
  • New Results from T2K Conclusively Show Muon Neutrinos Transform to Electron Neutrinos July 19, 2013 (Japan Edition)
    New results from T2K conclusively show muon neutrinos transform to electron neutrinos July 19, 2013 (Japan edition) T2K Collaboration High Energy Accelerator Research Organization (KEK) Institute for Cosmic Ray Research, The University of Tokyo J-PARC Center Today at the European Physical Society meeting in Stockholm, the international T2K collaboration announced definitive observation of muon neutrino to electron neutrino transformation. In 2011, the collaboration announced the first indication of this process, a new type of neutrino oscillation, then; now with 3.5 times more data this transformation is firmly established. The probability that random statistical fluctuations alone would produce the observed excess of electron neutrinos is less than one in a trillion. Equivalently the new results exclude such possibility at a 7.5 sigma level of significance. This T2K observation is the first of its kind in that an explicit appearance of a unique flavor of neutrino at a detection point is unequivocally observed from a different flavor of neutrino at its production point. In the T2K experiment in Japan, a muon neutrino beam is produced at the Japan Proton Accelerator Research Complex, called J-PARC, located in Tokai village, Ibaraki prefecture, on the east coast of Japan. The neutrino beam is monitored by a detector complex in Tokai and aimed at the gigantic Super-Kamiokande underground detector in Kamioka, near the west coast of Japan, 295 km (185 miles) away from Tokai. An analysis of the data from the Super-Kamiokande detector associated with the neutrino beam time from J-PARC reveals that there are more electron neutrinos (a total of 28 events) than would be expected (4.6 events) without this new process.
    [Show full text]
  • Simultaneous Analysis of Near and Far Detector Samples of the T2K Experiment to Measure Muon Neutrino Disappearance
    Simultaneous Analysis of Near and Far Detector Samples of the T2K Experiment to Measure Muon Neutrino Disappearance by Casey Bojechko B.Sc., University of British Columbia, 2007 A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY in the Department of Physics and Astronomy c Casey Bojechko, 2013 University of Victoria All rights reserved. This dissertation may not be reproduced in whole or in part, by photocopying or other means, without the permission of the author. ii Simultaneous Analysis of Near and Far Detector Samples of the T2K Experiment to Measure Muon Neutrino Disappearance by Casey Bojechko B.Sc., University of British Columbia, 2007 Supervisory Committee Dr. Dean Karlen, Supervisor (Department Physics and Astronomy) Dr. Mike Roney, Departmental Member (Department Physics and Astronomy) Dr. Scott McIndoe, Outside Member (Department of Chemistry) iii Supervisory Committee Dr. Dean Karlen, Supervisor (Department Physics and Astronomy) Dr. Mike Roney, Departmental Member (Department Physics and Astronomy) Dr. Scott McIndoe, Outside Member (Department of Chemistry) ABSTRACT The Tokai-to-Kamioka (T2K) experiment is a long-baseline neutrino-oscillation experiment that searches for neutrino oscillations with measurements of an off-axis, high purity, muon neutrino beam. The neutrinos are detected 295 km from production by the Super Kamiokande detector. A near detector 280 m from the production target measures the unoscillated beam. This thesis outlines an analysis using samples in the near detector and Super Kamiokande to measure the disappearance of muon neutrinos. To manage the complexity this analysis, a Markov Chain Monte Carlo framework was used to maximize a likelihood to estimate the oscillation parameters.
    [Show full text]
  • Tevatron Operations Review
    Plan for Fermilab: Fermilab Steering Group Report Young-Kee Kim Nov. 29, 2007, HEPAP On March 22, 2007, Steering Group formed by Pier Oddone to develop a roadmap for FNAL’s accelerator-based HEP program • Interim Status Report to HEPAP: July 13, 2007 • Internal Report to Pier Oddone: Aug. 7, 2007 • Final Report: Sep. 18, 2007 • Presentation to P5: Sep. 24, 2007 http://www.fnal.gov/directorate/Longrange/Steering_Public/ Outline 1. Guidelines in Forming the Plan developed by the Steering Group based on Charge 2. Physics with Intensity Frontier 3. Alignment with ILC 4. Intense Proton Facility Project X 5. Specific Physics Examples with Project X 6. Steering Group’s Proposed Plan Fermilab Plan and Project X, Young-Kee Kim, Nov. 29, 2007, HEPAP meeting Guidelines in forming the plan Developed by the Steering Group based on Charge Fermilab Plan and Project X, Young-Kee Kim, Nov. 29, 2007, HEPAP meeting Guidelines in forming the plan 1. The LHC program is our most important near-term project given its broad science agenda and potential for discovery. It is essential to support the physics analysis, computing, and accelerator and detector upgrades. Fermilab Plan and Project X, Young-Kee Kim, Nov. 29, 2007, HEPAP meeting Guidelines in forming the plan 2. The particle physics community’s highest priority for investment toward the future is the ILC, based on our present understanding of its potential for breakthrough science. Fermilab will continue to participate vigorously in the international R&D program for the ILC and to be one of the leaders in the global ILC effort.
    [Show full text]